This article discusses some of the additive manufacturing (AM) based fabrication of alloys and their respective mechanical, electrochemical, and in vivo performance. Firstly, it briefly discusses the three AM techniques that are most commonly used in the fabrication of metallic biomedical-based devices: binder jetting, powder-bed fusion, and directed-energy deposition. The article then characterizes the electrochemical properties of additive-manufactured/processed cobalt-chromium alloys. This is followed by sections providing an evaluation of the biological response to CoCr alloys in terms of the material and 3D printing fabrication. Discussion on the biological response as a function of direct cellular activity on the surface of CoCr alloys in static conditions (in vitro), in dynamic physiological conditions (in vivo), and in computer-simulated conditions (in silico) are further discussed in detail. Finally, the article provides information on the qualification and certification of AM-processed medical devices.

This article focuses on a study that was performed to understand the effects of powder attributes; process parameters; and hot isostatic pressing (HIP) treatment on the densification, mechanical and corrosion properties, and microstructures of 17-4 PH stainless steel gas- and water-atomized laser-powder bed fusion (LPBF) parts at various energy densities. The results from the study showed the strong dependence of densification, mechanical properties, and microstructures on temperature, pressure, and time during the HIP cycle. The density, ultimate tensile strength, hardness and yield strength of gas and water-atomized LPBF parts increased due to HIP treatment and were higher than as-printed properties. The results also confirmed superior corrosion performance of the HIP treated LPBF parts.

This article describes the Bayer process for the purification of alumina. The process includes four major stages: digestion, clarification, precipitation, and calcination. The article discusses the aluminum electrolytic process in terms of aluminum electrolysis cell design, magnetohydrodynamic forces, and cathode lining. It reviews the electrochemical reactions and thermodynamics for aluminum electrolysis standard Gibbs. The article also describes the cell operations and cell stability, as well as the key indicators of cell performance. It schematically illustrates the typical costs producing aluminum in an aluminum smelter. The article also discusses various environmental issues, such as fluoride recovery; perfluorocarbons, polycyclic aromatic hydrocarbons, and sulfur emissions; spent pot lining; and development of inert anodes and CO2 emissions.

Anodizing produces a uniform, continuous, highly ordered network of individual cells comprising a layer whose thickness and cell dimensions, and ultimately engineering properties, depend on the electrochemical parameters of the anodizing process. This article discusses the nucleation and growth of anodic aluminum oxide and the important characteristics of the finished porous anodic aluminum oxide. In industry, anodic oxides and the anodizing processes have been categorized into types that exhibit specific properties to suit specific applications. The article reviews the two most basic types of oxides, namely, barrier-layer anodic oxides and porous anodic oxides. It concludes with a description of postanodizing processes, such as dyeing and sealing.

This article reviews the corrosion interactions between biomedical alloys, in particular iron-base, titanium-base, and cobalt-base alloys, in complex geometries and in applications where there are significant cyclic stresses and potential for wear and fretting motion. It discusses the nature of these metal surfaces and their propensity for corrosion reactions when combined with similar or different alloys in complex restrictive environments within the human body and under loading conditions. The article describes the factors that influence mechanically assisted crevice corrosion. It reviews the tests developed to investigate the aspects of mechanically assisted corrosion of metallic biomaterials: the scratch test and the in vitro fretting corrosion test.

The interaction of an implant with the human body environment may result in degradation of the implant, called corrosion. This article discusses the corrosion testing of metallic implants and implant materials. The corrosion environments for medical implants are the extracellular human body fluids, very complex solutions containing electrolytes and nonelectrolytes, inorganic and organic constituents, and gases. The article describes the fundamentals of electrochemical corrosion testing and provides a brief discussion on various types of corrosion tests. It illustrates corrosion current density determination by Tafel extrapolation, potentiodynamic measurement of the polarization resistance, electrochemical impedance measurement, and potentiostatic deaeration. Tests combining corrosion and mechanical forces, such as fretting corrosion tests, environment-assisted cracking tests, and ion-leaching tests are also discussed.

This article reviews the understanding of corrosion interactions between alloys in complex geometries and in applications where there are significant cyclic stresses and potential for wear and fretting motion. These alloys include iron-base, titanium-base, and cobalt-base alloys. The article discusses the surface characteristics and electrochemical behavior of metallic biomaterials. It summaries the clinical context for mechanically assisted corrosion and describes mechanically assisted crevice corrosion. There have been several tests developed to investigate aspects of mechanically assisted corrosion. The article also explains the scratch test and the in vitro fretting corrosion test.

This article focuses on the various types of corrosion-related failure mechanisms and their effects on passive electrical components. The types include halide-induced corrosion, organic-acid-induced corrosion, electrochemical metal migration, silver tarnish, fretting, and metal whiskers. The passive electrical components include resistors, capacitors, wound components, sensors, transducers, relays, switches, connectors, printed circuit boards, and hardware.

This article provides information on various forms of corrosion that occur in electronic packaging. Portable consumer electronic hardware which is subjected to humidity exposures is prone to condensed moisture and liquid damage. The article discusses two other corrosion-related phenomena that are found only in electronics, namely, electrochemical migration (ECM) and conductive anodic filament formation (CAF). It describes the corrosion that takes place in metals such as copper, tin, and tin-lead alloys, which are commonly used in electronic packaging. The article also discusses the corrosion of the components used in electronic assemblies.

This article explores the use of the electrochemical and nonelectrochemical techniques for measuring the corrosion behavior of buried metals and the types of probes used. The electrical resistance technique is the main nonelectrochemical technique used for measuring corrosion rate. Electrochemical techniques discussed include linear polarization resistance, electrochemical noise, harmonic distortion analysis, electrochemical impedance spectroscopy, and hydrogen permeation. The principles of operation for the corrosion measuring techniques are described along with examples of their use in soils.

This article contains a galvanic series chart that shows the electrochemical voltage ranges of metals and alloys in flowing seawater. Dark boxes in the chart indicate the active behavior of active-passive alloys.

The rate and form of corrosion that occur in a particular situation depend on many complex variables. This article discusses the rate of corrosion of lead in natural and domestic water depending on the degree of water hardness caused by calcium and magnesium salts. Lead exhibits consistent durability in all types of atmospheric exposure, including industrial, rural, and marine. The article tabulates the corrosion of lead in various natural outdoor atmospheres and the corrosion of lead alloys in various soils. It explains the factors that influence in initiating or accelerating corrosion: galvanic coupling, differential aeration, alkalinity, and stray currents. The resistance of lead and lead alloys to corrosion by a wide variety of chemicals is attributed to the polarization of local anodes caused by the formation of a relatively insoluble surface film of lead corrosion products. The article also provides information on the corrosion rate of lead in chemical environments.

Overpotential is the current-producing potential difference between a nonequilibrium electrode potential and its corresponding equilibrium value for an electrode reaction. This article provides information on the overpotential of an electrode reaction. It contains a table that lists the values based on the electrode reaction. Because overpotential is a kinetic parameter and depends on current density, overpotential values presented are for a specific current density.

This article is a compilation of tables that list the standard reduction potentials for electrochemical reactions alphabetically by element of interest and potential value.

This article contains tables that list standard reduction potentials for electrochemical reactions. The first table lists reactions alphabetically by element of interest. The second table is ranked by potential value. Potential is measured versus the Standard Hydrogen Electrode which has a value of 0.0000 V. Reactions with more than one voltage indicate that results have not been reconciled. Parenthetical materials not needed to balance reactions are catalysts.

This article provides a summary of the concepts discussed in the articles under the Section “Fundamentals of Corrosion” in ASM Handbook, Volume 13A: Corrosion: Fundamentals, Testing, and Protection. In this section, the thermodynamic aspects of corrosion are descried first followed by a group of articles discussing the fundamentals of aqueous corrosion kinetics. The fundamentals of gaseous corrosion are addressed next. The fundamental electrochemical reactions of corrosion and their uses are finally described.

Electrochemical, or electrode, reactions occur with charge transfer between neutral or ionic reactants and a conducting material called the electrode. This article discusses cathodic reactions that result in reduction and anodic reactions that result in oxidation. It reviews the effects of an electric field near an electrode and illustrates the solvation of ions in metal-aqueous solution.

Principles of metallic corrosion play a fundamental role in developing industrial processes that employ corrosion for constructive purposes. This article examines the changes in kinetics that occur with differentially small potential changes around the equilibrium electrode potentials of two reversible electrodes, such as copper and silver electrodes, in an electrochemical system. It provides a schematic illustration of a reversible cell with copper and silver electrodes to determine a reversible cell potential between the electrodes. An electrode becomes irreversible when the electrode reactions are displaced from equilibrium and the electrode potential is no longer at the equilibrium potential. The article describes irreversible cell potential by using galvanic cells, electrolytic cells, and corrosion cells.

Electrode potential is a key parameter in the thermodynamic and kinetic processes that drive aqueous corrosion. This article discusses the complexities associated with measuring electrode potential and explains where and how to use reference electrodes to improve measurement accuracy. It describes a three-electrode approach that compensates for measurement error stemming from nonequilibrium conditions. It also examines electrode materials and behaviors and offers insights on selection and operating conditions.